yes all of the campaigns from Left 4 dead 1 have been ported into Left 4 dead 2 with the original characters and everything. The difference is those missions have melee weapons and the new Sepcial infected zombies added to them, which are not in the Left 4 Dead 1 version of those levels and some changes to the levels themeselfs.

If money is no object too you get both, if you can or prefer to only get one get l4d2, it has all the campagins besides 1 exclusive survival map in l4d, more weapons, and more infected. Some people say L4D is faaaaaaaaaaaaaaaar better. Personally im sticking with l4d2 since im poor but hey the choice is yours.

You shuld get L4D1 too, it's awesome. I love both games, but still, I think L4D1 is better in terms of gameplay. It contains the first game's campaigns, but they are modified, so thhat you can play them again :) First grab the first one, so that you'll enjoy both :)

L4d1 has much better VS game play and game mechanics are better thought out. If all you care about is the extra maps l4d2 will suffice. Otherwise you want l4d1.

I would like to offer an opposite view to Barry's. I think L4D2 has a much better VS mode. L4D1 has a point system were you get points for map completion with a survivor multiplier at the end. If whole team makes it 90% of the way then all but one dies, you get a point multiplier of 1x (ie no bonus). Then the entire other team makes it 100% of the way which earns them a multiplier of 4x. This leads to lopsided games, which leads to A LOT of rage quitting. In L4D2 most of your points come from map completion with slight bonus points at the end. This leads to closer, more competitive and intense games.